This proposal responds to the National Institutes of Health NIAID RFA:AI-96-OOl for renewal of the ongoing Pediatric AIDE Clinical Trial Group (PACTG), and specifically for the renewal of the Pediatric AIDS Clinical Trials Unit of the University of Washington/Children's Hospital and Medical Center of Seattle (UW PACTU). The UW PACTU began as a subunit of the UW Adult ACTU in 1989, became an independent PACTU in 1991, and is applying for renewal in conjunction with the Coordinating and Operations Center (CORC) headed by Stephen Spector, M.D. The UW PACTU has made major contributions to the PACTG through participation in trials and leadership of its faculty in protocol development, committee work and in contributions to the scientific agenda. The purpose of the UW PACTU is to perform exemplary clinical trials research in support of the PACTG. The proposal of the UW PACTU describes three specific aims: 1) To contribute to the scientific agenda of the PACTG by providing scientific leadership and proposing protocols aimed at understanding the viral pathogenesis of AIDS in relation to the prevention of perinatal (vertical) HIV-1 transmission; improving primary therapy of HIV-1 infection in children; improving treatment and prophylaxis of opportunistic infections; understanding immune recovery achieved when antiviral therapy is effective; and potential strategies for gene therapy. 2) To develop virologic and pharmacologic assays to better evaluate, predict and understand the course of HIV-1 and related infections. 3) To continue to enroll subjects in PACTG protocols, to follow subjects according to protocol, with the production of high quality clinical and laboratory data, and in compliance with the high regulatory standard: imposed by the ACTG and DAIDS. This will include continued recruitment of pregnant women and children of color into protocols, and the maintenance of linkages with community-based organizations, the Community Advisory Board (CAB) of the UW's PACTU/AACTU, and the medical community of Washington, Wyoming, Alaska, Montana, Idaho (WAMI) and northern Oregon. This proposal describes the scientific contributions of UW PACTU investigators to the PACTG and the anticipated scientific contributions during the next four years. The infrastructure and organization of personnel is described, including plan develop a UW PACTU Subunit at Oregon Health Sciences University (OHSU). The structure and role of the CAB and the linkages with community based organizations are described. The PACTG site reports and regulatory evaluations of the UW PACTU which have generally been excellent are discussed. This proposal requests funds for the continuation of the successful UW PACTU.